Hello to all, 

I believe some of you are in dilemma but I hope so meany of you are much more experience than I am. Making decision of changing bearing base on envelope alarms is not always the best approach but if all envelope filter are set up correctly and it is nice development of bearing fault frequency over life ob bearing what your you advice and do you have a reference to point out for correlation amplitude in envelope spectrum with level of fault in bearing. I am referring to regular roiling bearings and usual speed of 1500 RMP. I would like to avoid replacing bearing if there is not viable damage...I usually confirm it with time signal but also usually damage is to large. I am trying to correlate amplitude in envelope spectrum and bearing fault like; under surface fault amplitude, initial small visible surface present amplitude, and significant but not big surface envelope amplitude. What is your experience and do you have some references? 

I know about a general rule established for the severity assessment of enveloped spectra. This involves measuring the amplitude of the specific component defect (whether inner race, outer race, ball spin, cage defect frequencies or any combination of each) in dB above the carpet level of spectrum. Any other and what is your experience. 

Original Post

Hi,

I am using enveloping for deeper analysis but sometimes it doesn't needed or i mean it is confusing, i do usually basic TWF and Spectrum and i can get the bearing fault, usually before i go replacement of bearing i check the amount of impacting if it get worsen.

regards

Hello to all,

What we are referring here envelope analysis is something we use but not for making decisions in future, using it just as a tool of an early indication of a problem but most of the time we trust more TWF and Spectrum, interesting. Can we say envelope analysis is not so practical tool? 

Are you on about envelope acceleration or envelope alarms? 

Regarding enveloped acceleration, making a call on it alone is not always advisable. As for your comment about only wanting to make calls to repair if you can see the damage, then the thing is at that stage it's too late, but I imagine you have maintenance colleagues who don't believe in your diagnosis if they did see visible damage when you open a bearing. Sadly this is a common thing.

The experience will tell you that you use the various tools at your disposal. Time waveform velocity/acceleration fft, peakvue/envelope acceleration.

no one technology can cover all encountered faults. 

Costa Ilic posted:

Hello to all,

What we are referring here envelope analysis is something we use but not for making decisions in future, using it just as a tool of an early indication of a problem but most of the time we trust more TWF and Spectrum, interesting. Can we say envelope analysis is not so practical tool? 

Incorrect to say envelope analysis is not so practical tool. Totally Disagree.

The analysis is not done only on TWF or Spectrum or Some alarms or Overall values. It is a collective effort where you check all the parameters, at times you even check parameters other than vibration like temp, pressure, flow etc..

My point is only enveloping is not sufficient but missing enveloping from your machinery route is also not a smart decision.

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